It is known in the art of gear cutting to provide for machines which utilize an endless chain for carrying a series of cutting tools into engagement with a workpiece to shape the workpiece into a gear form. It is also known to arrange a series of cutting tools around a cylindrical body for forming gears.
Although existing gears cutting equipment does a very satisfactory job of shaping gear tooth profiles, such as those required for spur and helical gears, certain gear applications require a refinement of such equipment to provide a lengthwise "crowning" of individual tooth members of whatever gear is being manufactured. Crowning is a known feature of certain types of bevel gear making machinery (as shown, for example, in U.S. Pat. Nos. 2,352,689; 2,385,330; and 2,385,331), however, it is not believed to be known for other types of gear making machinery which provide for a movement of one or more rows of cutting tools in a flat plane through a tooth slot. For example, when a series of cutting tools are rigidly secured in one or more carriers which are advanced into engagement with a workblank, a generally straight cut is formed when viewed in the longitudinal (or lengthwise) direction of each tooth slot being shaped into the workpiece. In order to crown the side wall portions of such a straight cut, it is required that there be a deeper cut at the entry and exit ends of the tooth slot as a cutting tool advances into and out of the slot. It is a primary purpose of this invention to provide an improved mechanical arrangement for controlling positions of selected cutting tools as they advance through tooth slots of a workpiece to thereby provide for a desired depth of cut to thereby achieve crowning of the individual tooth profiles.
In accordance with a specific embodiment of the present invention, selected stock-removing tools of a gear cutting machine are held by a number of carriers articulated together to form an endless chain which can be advanced into engagement with a workpiece to form tooth slots for a spur or helical gear. Mounting means are provided for securing selected tools of the series for controlled movements relative to their respective carriers to thereby provide for precision cutting and shaping of gear tooth profiles as the selected tools are advanced through slots of the workpiece. Control means are associated with the carriers for controlling the positions of the mounting means relative to the carriers in a way which extends or retracts the selected tools during a cutting operation as the tools are brought into engagement with the workpiece. Each mounting means comprises a mounting block for receiving a stock-removing tool in fixed relationship thereto, and the mounting block is suspended in a novel way within a bore of an associated carrier with spring elements comprising flat ring elements which are fitted around the mounting block and within the bore of the carrier. The spring elements are arranged in parallel planes at right angles to the desired axis of motion for the tools. The use of such spring elements eliminates the need for bearings or bearing surfaces and provides for radial rigidity of the tool while permitting linear motion of the tool. In addition, this type of suspension of a tool provides for a more rapid response with less of a tendency to initially stick and then slip to a new position. A displaceable member is fitted within the carrier for contacting and moving the mounting means in accordance with the degree and type of precision shaping required, and each displaceable member is actuated, in turn, by a control bar which follows a cam surface provided on a relatively fixed portion of the gear machine. In this way controlled movements are dictated to the selected tools as the tools move through a work zone of the machine.
The mechanism of the present invention is very reliable in design and provides for a positive and known displacement of the selected cutting tools at exactly the right points of travel of each tool relative to a tooth slot of the workpiece. The use of spring elements for suspending the tools provides for a simple and highly reliable system for positioning and moving the tools. Individual components of the mechanism are designed to withstand the stresses and workloads associated with production manufacture of gears or similar type products. These and other advantages and features of the invention will become apparent in the more detailed discussion which follows, and in that discussion reference will be made to the accompanying drawings as briefly described below.